It has been proposed to deliver certain types of drugs to patients by inhalation of a powder as a delivery mechanism. One particular example uses diketopiperazine microparticles known as Technosphere® microparticles. The Technosphere microparticles have a platelet surface structure and can be loaded with a drug. See, for example, U.S. Pat. No. 5,352,461, issued Oct. 4, 1994 to Feldstein et al.; U.S. Pat. No. 5,503,852, issued Apr. 2, 1996 to Steiner et al.; U.S. Pat. No. 6,071,497, issued Jun. 6, 2000 to Steiner et al.; U.S. Pat. No. 6,428,771, issued Aug. 6, 2002 to Steiner et al.; U.S. Pat. No. 6,444,226, issued Sep. 3, 2002 to Steiner et al.; and U.S. Pat. No. 6,652,885, issued Nov. 25, 2003 to Steiner et al. One use of these microparticles is the delivery of insulin by inhalation. An inhaler having a replaceable cartridge or capsule containing the drug powder is used for drug delivery.
The administration of drugs by inhalation typically requires a very small quantity of powder in the inhaler cartridge. By way of example, application of insulin using Technosphere microparticles can require a dose of as little as 10 milligrams of the powder. In addition, the drug dose must be highly accurate. A dose lower than specified may not have the desired therapeutic effect, while a larger than specified dose can have an adverse effect on the patient. Furthermore, while Technosphere microparticles are highly effective for drug delivery by inhalation, their platelet surface structure causes Technosphere powders to be cohesive and somewhat difficult to handle.
In the commercialization of drug delivery by inhalation, large numbers of cartridges containing the drug must be produced in an efficient and economical manner. An accurate dose of powder must be delivered to each cartridge, and the drug dose in each cartridge must be verified. Manufacturing techniques and equipment should be capable of high throughput to meet demand and should be capable of handling powders which are cohesive and thus do not flow freely. Existing manufacturing techniques and equipment have not been adequate to meet these demands.
Accordingly, there is a need for novel methods and apparatus for powder dispensing and sensing.